The "Glee" co-stars were spotted checking in for a flight together on Friday morning at Los Angeles International Airport. According to a source who spoke to E! News, 30-year-old Monteith first flew from the Caribbean island of Antigua (where he had been receiving treatment) to New York by himself and met up with Michelle, 26, in Los Angeles. The two were "very happy, smiling the entire time," said a witness.

Shortly after Monteith's rep revealed, on March 31, that the actor was voluntarily seeking treatment for substance addiction, Michele -- who has been dating Monteith for more than a year -- announced she’d proudly stand by her man: "I love and support Cory and will stand by him through this," she told People. "I am grateful and proud he made this decision."

This isn’t Monteith’s first time seeking treatment. He shared past struggles with drug abuse during a 2011 interview with Parade magazine, revealing that he “had a serious problem” and that his mother and friends staged an intervention when he was 19, three years after he had dropped out of high school.

“That’s when I first went to rehab. I did the stint but then went back to doing exactly what I left off doing,” he told Parade. Later, he stole money from a family member, an act he knew would get him caught. “I was so desperate I didn’t care. It was a cry for help," he said in the 2011 interview. "I was confronted and I said, ‘Yeah, it was me.’ It was the first honorable, truthful thing that had come out of my mouth in years.”

Monteith will be written out of the final few episodes of the current season of “Glee,” but his co-stars have shown nothing but support for him, with actress Jane Lynch especially understanding what he’s going through. She recently marked 21 years of sobriety. “I think you get to a point -- and this has happened to me -- [where] you decide to renew your vows to your sobriety,” the 51-year-old told AccessHollywood.com this week. “I think [Monteith] is renewing his vows to his sobriety.”